This program involves an analysis of some of the parameters associated with aging. The structural and molecular basis for the decline in mitochondrial activity will be explored using enzymatic assays, measurement of metabolic flux and transport of ions across the membrane and electron microscopy. The biogenesis of mitochondria will be explored in regenerating liver and hypertrophic heart. These studies will be carried out with rats, blowflies and nematodes. Investigations will be made on fibroblasts in serial culture on their viability and potential to secrete collagen. The fibroblast cultures will be from rats and long and short-lived teleosts. The collagen secreted by old cultures will be examined for primary sequence errors arising in biosynthesis.